Power system



May 9, 1939- G. F. SMITH 2,157,869

POWER SYSTEM Filed OCT.. 3l, 1936 WITN ESSES: '/'l ATTORN EY I4 lNvENoR erad .57m/277.

Patented Mey e, 1939 UNITED STATES rowcn srsm Gerald F. Smith, Forest Hills, Pa.. aloilnoto Westinghouse Electric Manufacturing Colnpan'y, East Pittsburgh, Pa.a corporation of N Pennsylvania Application october ai, 193s, sel-m No. meer -4 claims.

My invention relates, generally, to power systems for self-propelled vehiclesand, more particularly, to power systems wherein an internalcombustion engine drives an electric generator which supplies current for operating electric motors to propel the vehicle.

The present invention constitutes an improve ment over the system disclosed in my Patent 1,730,340, issued October 1, 1929, in which an engine drives a generator and an exciter for the generator, the exciter having a differential winding on a portion oi its poles which is energized by the main generator current in order to produce certain operating characteristics in the electricai machines which improve the perfomance.

of the Diesel or gas engine.

An object oi' the present invention is to improve the engine loading characteristics ci a power system in which an internai-combusti0n engine is utilized as the prime mover.

Another object of the invention is to maintain a predetermined speed of the prime mover of a self-propelled vehicle.

Other objects of the invention will be explained 555l fully hereinafter or will be apparent to those skilled in the art.

m accordance with one embodiment o! the present invention aA portion oi' the iield poles on the exciter for a power-generating system, comprising an engine, a generator and an exciter for the generator, are provided with a separately 0X- cited shunt field winding and the remaining poles are provided with a diiierential Winding which is energized by the main generator load current, as

in the system described in my aforementioned patent. In addition to the dilerentlal winding, these poles are also provided with a cumulative winding which is connected in series with the exciter armature circuit to improve the engine 4o loading characteristics, as will be explained more v fully hereinafter.

For a fuller understanding of the nature and objects of the invention, rei'erence may he had to the following detailed description, taken in conjunction with the accompanying drawing in which:

Figure 1 is a diagrammatic view of a power system for self-propelled vehicles embodying my invention;

Fig. 2 is a diagram ci connections used in the' power system;

Fig. 3 is a curve showing operating characteristics oi the power system;

u Fig. 4 is a diagrammatic view of a modified form of a power systemsimilar to the one shown in Fig.

; and

Fig. 5 is a diagram o the connections used in the modiiication of the invention shown in Fig. c.'

. Referring now to the drawing, and particularly s to Figs. 1. 2 and 3, the power system illustrated comprises an internal combustion engine lo which drives a generator il and an exciter i2 for the generator I l. by means oi a shaft i2. The generator Il may be utilized to furnish power for opi@ erating a motor i I which is suitable lor propelling a locomotive or other vehicle (not shown).

As described in foregoing Patent No. 1,730,340, the exciter i@ is provided with a pine rality of iield palm lli to so, inclusive. Four of the poles, Il to le, inclusive, are provided with separately excited windings lli which magico onere gized from a battery il?. An adjustable rhcostet 23 may be utilized for adjustingtiie bcurrent in theliield windings El. 'Lillie other two poles, il and 2G, are provided with diderentiai windings 2t which are connected in series=circuit relation with the armature ci the decorator i0 and are energized by the current in the load circuit lor the generator.

It will be understood that the windings ill and 2t function in the same manner as descrilced in my foregoing patent, the didereotlal windlncs 2d opposing the iiux established icy til-e windings si, thereby causing the exciter to have certa-ln citer lo acteristics similar to the exciter utilised in the system disclosed in my prior potent.

In order to improve tire engine loading characteristics of the system, l have provided smother winding 20 on the field poles i@ and 2). Tire c5 winding 28 is connected in series-circuit relation with the field winding il or' the generator il, which is connected across the armature 2G oi the exciter I2. Therefore, the generator n ex cited in accordance with the voltage developed oy ce the exciter i2, a rlieostat 2li being provided lor adjusting the generator dolci current and the winding 26 is energized los* the generator iielcl current. The addition ci the cumulative ilcld winding 28 to the poles lo and i@ does not reistel ce rially change the exciter-voltage generator-am peres characteristic ci the machines which re mains practically the come as for the machines described in my prior patent.

However, the torque-sd characteristic ofi the so present machines is as shown by the full line curve in Fig. 3. In this instance the torque decreases approximately as the square of the speed instead ci directly as the speed, asin the system described in my prior patent and indicated by the dotted line in Fig. 3. Therefore, the speed of the engine is maintained practically constant, since with a decrease in engine output, and a consequent decrease in engine speed, the torque falls rapidly "to minimize the speed decrease by automatically unloading the engine. It will be seen from the curve in Fig. 3 that this decrease in torque is rapid at high speed and full load, where it is most effective in maintaining a predetermined engine speed.

in the modiiication ci the invention shown in Figs. 4 and 5, a cumulative held winding 3i is added to each of the poles l5 to it, inclusive, in addition to the separately excited winding 2i, previously described. The windings il are connected in series-circuit relation with the diierential windings 2li and are energized by the current in the generator load circuit. f.

The cumulative windings 3l are utilized to provide a lower rio-load exciter voltage. Since the cumulative effect produced bg the windings Si depends upon the generator load current, it is evident that at no-load the windings 3i produce no flux and therefore, the exciter voltage is reduced at rio-load. The winding 26 on the poles ig and 2@ functions in the manner described hereinbefore to decrease the torque on the engine in the event of a decrease in speed, thereby maintaining a predetermined engine speed.

It will be understood that the desired operating characteristics may be obtained in a power system of the type herein described by providing the generator, instead of the exciter, with diiierential and cumulative eld windings as described hereinbeiore. Therefore, my invention is not limited in its application to machines utilized as exciters 'but may be applied to any dynamo-electric machine.

Furthermore, it is evident that the improved operating characteristics of a power system of the type herein described may be obtained by utilizing a split pole dynamo-electric machine in which the cumulative winding 26 is disposed on only a portion of the pole structure of each pole on the machine, thereby obtaining the same magnetic effect as in the structures herein de-a scribed. v

From the foregoing description it is evident that i have improved the engine loading characteristics of a power system in which an internal-combustion engine is utilized as the prime mover, thereby maintaining a predetermined speed oi the engine, which improves its operating efficiency.

Since numerous changes may be rnade in the above-described construction, and different ernbodiments oi the invention` may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illus-1 trative and not in a limiting sense.

I claim as my invention:

1. An exciter for energizing the eld winding of an engine-driven generator'for supplying current to a load circuit, said exciter being driven by the engine and provided with an armature winding connected in series-circuit relation with the iield winding of the generator, a separately excited field winding, a differential field winding energized by the current in said generator load circuit, and a cumulative field winding connected in series-circuit relation with the exciter armature winding.

2. An exciter for energizing the field winding of an engine-driven generator for supplying current to a load circuit, said exciter being driven by the engine and provided with an armature winding connected in series-circuit relation With the eld winding of the generator, a separately excited field winding disposed on a portion of the ield poles of the exciter, a differential leld winding disposed on the remaining eld poles of the exciter and energized by the current in. said generator load circuit, and a cumulative eld winding connected in series-circuit relation with the exciter armature winding.

3. An exciter for energizing the leld winding of an engine-driven generator for supplying current to a load circuit, said exciter being driven by the engine and provided with an armature winding connected in series-circuit relation withthe field winding of the generator, a separately excited eld winding disposed on a portion of the field poles oi the exciter, a differential eld winding disposed on the remaining field poles of the exciter and energized by the current in said generator load circuit, and a cumulative neld winding disposed on the same poles as the difierential eld winding and connected in seriescircuit relation with the exciter armature winding.

4. An exciter for energizing the iield winding of an engine-driven generator for supplying current to a load circuit, said exciter being driven by the engine and provided with an armature winding connected in series-circuit relation with the eld winding of the generator, a separately excited field winding disposed on a portion of the field poles of the exciter, a diierential eld winding disposed on the remaining iield poles of the exciter and energized by the current in said generator'load circuit, a cumulative field winding disposed on the same poles as the differential iield winding and connected in seriescircuit relation with the exciter armature winding, and an additional cumulative iield winding disposed on the same poles as the separately excited winding, said additional winding being energized by the current in the generator load circuit.

GERALD F. SMITH. 

